Adjustable driving wheels

ABSTRACT

An adjustable driving wheel comprises a central holder having a variable diameter wheel periphery provided by blocks slidable on pairs of parallel rods radiating from the central Holder at uniformly spaced intervals around it, the blocks being movable simultaneously inwardly and outwardly by means of a rotary cam positioned at one side of the wheel.

O United States Patent 1151 3,661,024 Cooke May 9, 1972 [54] ADJUSTABLE DRIVING WHEELS 742,497 10/1903 Rowand ..74/230.23 858,754 7/1907 Reed ...74/230.23 [72] Invent Edward Cmke Lemme" England 3,279,271 lO/l966 Sackl ..74/230.23 [73] Assignee: Trip-Lite Limited, Leicester, England [22] Filed: Jun 1 1970 Primary E.\-aminerC. J. Husar 1 pp No 46 340 Att0rneyLarson,Tayl0r & Hinds [30] Foreign Application Priority Data [57] ABSTRACT June 20, 1969 Great Britain 3 1,213/69 An adjustable driving wheel comprises a central holder having a variable diameter wheel periphery provided by blocks slidas21 U.S. c1 ..74/230.23 Pairs of Paranel mds radiaing fmm central [51 1 Int Cl Fl6h 55/54 at uniformly spaced intervals around it, the blocks being i i movable simultaneously inwardly and outwardly by means of a [58] Field of Search 74/213023, 230.18, 230.19 rotary cam positioned at one Side ofthe wheeL [56] References Cited 7 Claims, 3 Drawing Figures UNITED STATES PATENTS 896,160 8/1908 Rosenwarne ..74/23Q.23

PATENTEDMAY 9 m2 SHEET 2 [IF 2 mm om ADJUSTABLE DRIVING WHEELS This invention is for improvements in adjustable driving wheels and has for one of its objects to provide a wheel for driving a band, tape or the like with the facility for continuous and accurate variation in the effective diameter of the wheel.

In accordance with the invention there is provided an adjustable driving wheel comprising a central holder having an expansible wheel periphery around it and adjustable cam means for varying the effective diameter of the wheel periphery, characterized by having mounted on the holder uniformly spaced radial pairs of parallel spokes in the form of rods and by having blocks slidably mounted each on a pair of the rods and forming a skeleton periphery to the wheel the cam means being positioned alongside said blocks to act on them to move them simultaneously inwardly and outwardly of the wheel to vary its effective diameter. Thus the wheel can be adjusted to drive a driven member through a band, tape or the like at difierent speed ratios by adjustment of the cam means.

In a convenient construction the cam means is provided on a disc alongside the blocks which may extend radially from the central holder to approximately the same extent as the blocks. The cam means may be formed as a recess or slot or a plurality thereof, in such disc which thus forms a circular face cam. The band, tape or the like is arranged to extend partly round the wheel between the end parts of the spokes in each pair which project beyond the radially adjustable blocks. Additional side guards may be provided by the said disc on which the cam means is provided on the one hand and a protective cover in the form of a plain disc fitted at the other side of the wheel on the other hand. A further protective disc may be provided beyond the first main disc as a second protective cover to exclude foreign matter if desired.

The aforesaid cam means may take the form of a single spiral recess or slot formed in the first mentioned disc in which are engaged lateral projections on the radially adjustable blocks. Such projections, being caused to engage the single spiral slot at different positions therein, need to be offset radially of the wheel from one block to another in order to provide that the outer faces of the blocks are mounted in a circular arrangement concentric with the wheel axis. Advantageously however there are formed a number of spirally arranged slots corresponding in number to the number of adjustable blocks and spaced apart in similar arrangement around the axis of the disc so as to operate simultaneously on the blocks when the disc is turned relatively to the central holder. In this case each block will have its projection in the same place.

"It is advantageous with the cam means constituted by a slot or slots in the cam disc for the projections to be formed by spring loaded pins with tapered ends which are urged resiliently into engagement with both sides of the slot or their respective slots to ensure that there is no play between the projections and the cam slot or slots in the radial direction.

The disc that is provided with the cam means may be formed peripherally with gear teeth for engagement by a spur gear to effect adjustment of the disc rotationally with respect to the blocks. With the central holder attached to and positioned between two discs the disc carrying the cam means may be a third disc mounted to turn relatively to the holder about the axis thereof and positioned between one of the first said discs and the blocks, and the last mentioned one of the first said discs may support peripherally a stub spindle to which is fixed a spur gear engaging with the gear teeth on the cam carrying disc.

Two convenient forms of construction in accordance with the invention are illustrated by way of example in the accompanying drawings in which FIG. 1 is an elevation view of one form of the adjustable driving wheel as seen looking in a direction at right angles to its axis,

FIG. 2 is an elevation view showing the cam disc and other parts as viewed looking downwardly on FIG. 1, and

FIG. 3 is a perspective view showing a more developed form of the driving wheel.

In FIGS. 1 and 2 of the drawings the central holder is shown at 10 and it is equipped with pairs of parallel rods 11 forming the spokes as aforesaid secured to the holder 10 at uniformly spaced intervals around its circumference. On the rods 11 are slidably mounted blocks 12 which are movable radially of the wheel and together make up the effective periphery of the wheel which engages the band, tape or the like which is confined between the projecting outer ends of the rods 11. The blocks 12 are equipped with projections in the form of pins having tapered ends seen at 13 the bodies of the pins being contained in blind apertures in the blocks and backed by springs. The tapered ends 13 of the pins engage in spiral slots 14 formed in a cam disc 15 which is mounted on a part of the holder '10 in such a way as to be rotatable therewith during normal operation but also rotatably adjustable relative to holder 10 to change the angular position of disc 15 relative to holder 10, rods 1 l and blocks 12 thereon. There is a spiral slot 14 for each block 12 to be engaged by the tapered end 13 of its pin. Thus by turning the disc 15 relative to elements l0, l1 and 12 all the blocks are adjustable together radially inwards or outwards depending upon which way the disc 15 is directed.

On the side of the blocks 12 opposite to the disc 15 there is a projecting disc 16 which may be fixed to the holder 10. If desired a similar disc to that shown at 16 may be fitted on the outside of the disc 15 beyond the position to which the tapered end 13 projects.

'To ensure easy movement of the blocks 12 along the rods 11 each block is formed with a circular hole 17 of a size to provide for a sliding fit on one of the rods and an open ended slot 18 to fit on to the other rod with the sides of the slot 18 having a sliding fit on the rod.

In the construction of FIG. 3, the variable diameter pulley is shown at 20 and is mounted on a vertical shaft 29. It comprises radially adjustable blocks 21 slidable on pairs of parallel radial spokes 22 radiating from a central holder 23, and a cam disc 24, all as in the first construction described. The pulley 20 drives a positive feed spindle through a belt 19. By turning the disc 24 relatively to the holder 23 the blocks 21 are adjusted radially to vary the effective diameter of the pulley presented by the center parts of the blocks 21 engaged by the belt 19 between projecting ends of the rods 22. The cam disc 24 is formed with gear teeth 25 around its edge which are engaged by a pinion gear 26 turning of which causes adjustment of the disc 24 and of the effective diameter of the pulley 20.

It will be understood that while the central holder 23 of the pulley 20 is fixed to the vertical shaft 29, the cam disc 24 is mounted so as to be capable of turning on the shaft. Also fixed to the shaft 29 there is a carrier disc 27 which supports on four pillars (two of which are seen at 28) a stepping motor used for adjustment of the cam disc 24. This motor has a spindle 30 which carries a gear wheel 31 for driving through a train of gears 32 a gear wheel 33 secured to a spindle to which the pinion 26 is fixed. The gears 32 and 33 have their spindles carried by the canier disc 27.

The pulley assembly may have (for resetting purposes) a bracket 52 fixed to the cam disc 24 and having an upturned wing 53 arranged to trip a button 54 of a micro-switch 55 supported by a bracket 56 having a clamping screw 57 by which it can be fixed to the carrier disc 27 at any desired position around the periphery thereof.

It will be seen that in the construction of FIG. 3, the pulley 20 comprises a central block supporting the spokes 22 and upper and lower discs all fixed to the shaft 29 to rotate therewith and a third disc constituted by the cam disc 24 interposed between the block 23 and disc 27 and mounted to rotate relatively to the shaft 29.

In both of the constructions illustrated it is advantageous to have as shown, each of the blocks 12 or 21 pierced with a clearance hole to slide on one of the spokes 11 or 22 and formed with'a slot extending to an adjacent edge of the block to slide freely on the other of the spokes 11 or 22. Thereby it can be ensured that no binding of the blocks 12 or 21 on the spokes 11 or 22 can arise from canting of the blocks, and a very smooth and accurate adjustment action is made possible.

What we claim is 1. An adjustable driving wheel comprising in combination a central holder, pairs of parallel rods connected to and projecting radially from said holder at positions spaced uniformly around it, a set of blocks slidably mounted one on each pair of the rods and together forming a skeleton periphery of the wheel, and cam means positioned alongside said blocks and movable rotatably for moving the blocks simultaneously radially inwardly and outwardly of the wheel axis to vary its effective diameter, said cam means comprising a cam disc at one side of the wheel, spirally arranged slots formed in the cam disc, the slots corresponding in number to the number of adjustable blocks and being spaced apart in similar arrangements around the axis of the disc, with each of said slots engaging a projection on its corresponding block.

2. A driving wheel according to claim 1, wherein the outer end parts of the rods in each pair of parallel rods project beyond the radially adjustable blocks to receive a band, tape or the like between them extending partly round the wheel against the outer faces of the blocks.

3. A driving wheel according to claim 2 having side guards provided by said cam disc of the cam means on one side of the wheel and a plain disc at the other side of the wheel.

4. A driving wheel according to claim 1 wherein the projections on the blocks are formed by spring loaded pins with tapered ends which are each urged resiliently into engagement with both sides of its corresponding in the cam disc.

5. A driving wheel according to claim 1 having the cam disc formed peripherally with gear teeth for engagement by a spur gear to effect adjustment of the disc rotationally with respect to the blocks.

6. A driving wheel according to claim I having first and second discs attached to the central holder on opposite sides thereof, and having the cam disc as a third disc mounted to turn relatively to the holder about the axis thereof and positioned between said second disc and the holder and blocks, and having a stub-spindle rotatably mounted on the said second disc at the periphery thereof, and a spur gear fixed to said stub spindle and engaging with the gear teeth on the cam disc.

7. A driving wheel according to claim 1 wherein each of said blocks is formed with a hole to slide on one of its two parallel rods and formed with a slot extending to the adjacent side of the block to slide freely on the other of its parallel rods. 

1. An adjustable driving wheel comprising in combination a central holder, pairs of parallel rods connected to and projecting radially from said holder at positions spaced uniformly around it, a set of blocks slidably mounted one on each pair of the rods and together forming a skeleton periphery of the wheel, and cam means positioned alongside said blocks and movable rotatably for moving the blocks simultaneously radially inwardly and outwardly of the wheel axis to vary its effective diameter, said cam means comprising a cam disc at one side of the wheel, spirally arranged slots formed in the cam disc, the slots corresponding in number to the number of adjustable blocks and being spaced apart in similar arrangements around the axis of the disc, with each of said slots engaging a projection on its corresponding block.
 2. A driving wheel according to claim 1, wherein the outer end parts of the rods in each pair of parallel rods project beyond the radially adjustable blocks to receive a band, tape or the like between them extending partly round the wheel against the outer faces of the blocks.
 3. A driving wheel according to claim 2 having side guards provided by said cam disc of the cam means on one side of the wheel and a plain disc at the other side of the wheel.
 4. A driving wheel according to claim 1 wherein the projections on the blocks are formed by spring loaded pins with tapered ends which are each urged resiliently into engagement with both sides of its corresponding in the cam disc.
 5. A driving wheel according to claim 1 having the cam disc formed peripherally with gear teeth for engagement by a spur gear to effect adjustment of the disc rotationally with respect to the blocks.
 6. A driving wheel according to claim 1 having first and second discs attached to the central holder on opposite sides thereof, and having the cam disc as a third disc mounted to turn relatively to the holder about the axis thereof and positioned between said second disc and the holder and blocks, and having a stub-spindle rotatably mounted on the said second disc at the periphery thereof, and a spur gear fixed to said stub spindle and engaging with the gear teeth on the cam disc.
 7. A driving wheel according to claim 1 wherein each of said blocks is formed with a hole to slide on one of its two parallel rods and formed with a slot extending to the adjacent side of the block to slide freely on the other of its parallel rods. 